JPS6018598Y2 - diesel engine fuel injection system - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a fuel injection device for a diesel engine.

Conventionally, diesel engine fuel injection systems have been designed to delay the fuel injection timing during low and medium loads to reduce NOx and noise, while advancing the fuel injection timing during high loads to ensure sufficient output. It has been proposed to install a so-called road timer, which is a device that adjusts the fuel injection timing according to changes in load.

However, when operating a diesel engine equipped with such a device at high altitudes where atmospheric pressure has decreased,
As the amount of air filling the combustion chamber decreases and the ignition delay increases, combustion becomes incomplete, especially when the engine is under low load, and fuel injected into the combustion chamber is discharged unburned into the exhaust gas. , a problem arises in that a so-called half-misfire phenomenon occurs.

Therefore, in order to deal with such ignition delays at high altitudes, conventional methods have been to advance the injection timing by increasing the oil pressure in the pump chamber, as disclosed in, for example, Japanese Patent Laid-Open No. 55-84824. is proposed.

However, although this proposal has the advantage that the injection timing advances uniformly, it has the disadvantage that the advance angle is small especially in the low rotational speed range, which is a problem, and the disadvantages caused by ignition delay cannot be sufficiently eliminated.

On the other hand, if the injection timing is advanced as much as necessary at low engine speeds, it will advance too much at high engine speeds, causing problems such as noise.

The present invention was developed in view of the above problems, and includes a cam device that reciprocates a plunger that pumps fuel, and an injection timing that adjusts the fuel injection timing by operating the cam device with oil pressure that corresponds to the engine rotation speed. A pressure detection device for detecting atmospheric pressure in a diesel engine fuel injection device comprising an adjustment device and a hydraulic control device that lowers the oil pressure and delays fuel injection timing when the engine load is small;
A restraint device is provided to reduce the hydraulic pressure lowering function of the hydraulic control device, and when the pressure detection device detects a decrease in atmospheric pressure, the restraint device is activated to advance the fuel injection timing compared to when the load is low on flat ground. It is an object of the present invention to provide a fuel injection device for a diesel engine that solves the above-mentioned conventional problems.

Hereinafter, the present invention will be explained in detail based on drawings showing embodiments.

In the distribution type fuel injection pump 1 shown in FIGS. 1 and 2, 2 is a housing, 3 is a drive shaft driven by the engine crankshaft (not shown) at a rotation speed of 172, and 4 is formed in the housing 2. pump room, 5
is a suction passage that connects the pump chamber 4 to a fuel tank (not shown).

6 is a vane type feed pump interposed in the middle of the suction passage 5, and is driven by the drive shaft 3.

By driving this feed pump 6, fuel from the fuel tank is fed under pressure to the pump chamber 4 via the suction passage 5,
The internal pressure within the pump chamber 4 is configured to increase as the rotational speed of the drive shaft 3, that is, the engine rotational speed increases.

Reference numeral 7 denotes a pump/distribution plunger, which is slidably inserted into a sliding hole 8 formed in the housing 2.

A cam disk 9 on which a cam surface 9a having a number of peaks corresponding to the number of cylinders of the engine is formed is integrally connected to the end of the plunger 7, and the drive shaft 3 is connected to the driving disk. (not shown).

A roller holder 10 is provided in the housing 2 so as to be rotatable and concentric with the drive shaft 3, and includes a cam disc 9.
The number of rollers 11 equal to the number of ridges on the cam surface 9a (that is, the number corresponding to the number of cylinders) is rotatably held.

The cam surface 9a of the cam disc 9 is pressed against the roller 11 by a plunger spring (not shown), and as the cam disc 9 rotates on the roller 11,
The plunger 7 is configured to simultaneously perform reciprocating motion for sucking and pumping fuel and rotational motion for distributing fuel.

Therefore, when the plunger 7 is in the suction process (downward movement in FIG. 1), the combustion in the pump chamber 4 flows from the supply passage 12 formed in the housing 2 to the plurality of vertical lines provided on the outer peripheral surface of the head of the plunger 8. It is supplied to the plunger chamber 29 via one of the grooves 13 (four in this example).

Further, when the plunger 7 moves to the pressure feeding process (increasing movement in FIG. 1), the communication between the supply passage 12 and the vertical groove 13 is severed, and the fuel in the plunger chamber 29 is compressed, and the fuel formed in the plunger 7 is It is supplied from the vertical hole 14 through the distribution horizontal hole 15 to one of the discharge passages 17 having check valves 16 formed in the housing 2 in a number corresponding to the number of cylinders in the circumferential direction,
It is injected into the cylinder from an injection nozzle (not shown).

Reference numeral 18 denotes a cut-off sleeve, which fits into the vertical hole 14 of the plunger 7 at a portion of the plunger 7 that protrudes toward the pump chamber 4 side.
It is slidably fitted onto the outside so as to open and close a cut-off port 19 that communicates with the cut-off port 19 .

When the cutoff port 19 is removed from the upper edge of the cutoff sleeve 18 and opens into the pump chamber 4, fuel flows into the pump chamber 4 and stops being discharged to the discharge passage 17, forming an injection path.

A flyweight 20 is connected to a flyweight holder 30 that is integrally fixed to the gear 21.

This holder 30 is attached to the governor shaft 22, and is driven by a drive shaft 3 to which a gear (not shown) that meshes with the gear 21 is fixed.

Also, the movement of the fly weights 20 is controlled by the governor shaft 2.
Governor sleeve 23 slidably inserted into the small diameter portion of No. 2
transmitted to.

A relief port 24 is opened in this governor sleeve 23, and when the governor sleeve 23 is in a low/medium load position where the amount of fuel injection is small, the port 24 is communicated with the horizontal hole 25 of the governor shaft 22, thereby, Pump room 4
However, the relief port 24, the horizontal hole 25, and the governor shaft 2
It is connected to the suction side (low pressure side) of the vane type feed pump 6 through the vertical hole 26 of No. 2 and the relief passage 27 .

A solenoid valve 28 is provided in the relief passage 27 to open and close the passage 27, and is connected to the battery 62 via an atmospheric pressure detection switch 60 and a key switch 61 that is turned on during engine operation.

The atmospheric pressure detection switch 60 is controlled on/off by a bellows 63 whose interior is evacuated or gas is sealed, and is atmospheric pressure or atmospheric pressure introduced into a chamber 64 around the bellows 63. When the pressure in the engine intake passage (not shown) related to the engine becomes low, the bellows 63
extends and turns off the switch 60.

Therefore, when the engine is operated on level ground, the key switch 61 and the atmospheric pressure detection switch 60 are turned on, the solenoid valve 28 is energized, the relief passage 27 is opened, and the movement of the governor sleeve 23 causes the pump to pump at low and medium loads. The fuel pressure (hydraulic pressure) in the chamber 4 is reduced and the fuel injection timing is adjusted to the delayed side by the movement of a timer piston 46, which will be described later.

On the other hand, when the engine is operated at a high altitude, the atmospheric pressure detection switch 60 is turned off and the solenoid valve 28 is not energized to close the relief passage 27. Even during low/medium load conditions, the oil pressure in the pump chamber 4 does not decrease, and the injection timing is advanced compared to that on flat ground.

Reference numeral 32 denotes a governor lever assembly, in which one end of a tension lever 33 and a start lever 34 are pivotally supported by a pin 35 on a collector lever (not shown), and a cut-off sleeve 18 is mounted on one end of the start lever 34. A Rad pin 37 is attached to the ball engaged in the engagement groove.

A start spring 38 is fixed to the other end of the start lever 34 and is interposed between the levers 33 and 34.

39 is a governor spring, one end of which is attached to the tension lever 33 via a pin 40, and the other end is a control lever 41 that is linked to an accelerator pedal (not shown).
is connected to a rotation shaft 42 via a shackle 43.

The position of the cutoff sleeve 18, ie, the amount of fuel injected, is determined by the rotation angle of the control lever 41 and the centrifugal force (engine rotation speed) of the flyweight 20.

A timer 44 controls the fuel injection timing, and has a timer piston 46 that slides within a cylinder 45 formed within the nozzle housing 2.

This timer piston 46 is connected to the roller holder 10 via a lever 48 that is swingable about a fixed shaft 47.

Further, a spring 49 is compressed on one side of the cylinder 45, sandwiching the timer piston 46, and a first hydraulic chamber 50 to which fuel pressure on the suction side of the feed pump 6 acts is formed, and a timer piston 46 is formed on the other side. A second hydraulic chamber 52 is formed to which the fuel pressure of the pump chamber 4 acts via a hydraulic passage 51 provided in the piston 46 .

The differential pressure between the first hydraulic chamber 50 and the second hydraulic chamber 52, that is, the fuel pressure corresponding to the engine rotation speed, and the spring 4
9 determines the position of the timer piston 46, that is, the circumferential position of the roller holder 10 via the lever 48, and the contact position between the roller 11 and the cam surface 9a of the cam disk 9 changes. A relative change occurs between the circumferential phase of and the contact position, that is, the operating position of the plunger 7, and the oil feeding pressure of the feed pump 6,
That is, the fuel injection timing is advanced as the engine speed increases.

With the above configuration, when the engine is operated on a flat ground where the atmospheric pressure is normal, the solenoid valve 28 opens the relief passage 27 because the atmospheric pressure detection switch 60 is on.

Therefore, when the engine load is small, the tension of the governor spring 39 is weak, so the flyweight 20 moves the governor sleeve 23 upward (in FIG. 1), and the horizontal hole 25 of the governor shaft 22 and the governor sleeve 23 Since the relief ports 24 coincide and communicate the pump chamber 4 with the feed pump upstream (low pressure side) via the relief passage 27, the pressure inside the pump chamber 4 decreases.

Along with this, the pressure in the second hydraulic chamber 52 of the timer 44 also decreases, so the timer piston 46 is pulled back to the delay side by the elastic force of the spring 49.

When the engine load exceeds the set value and the fuel injection amount increases, the governor sleeve 23 moves downward (in Fig. 1), the relief port 24 and the horizontal hole 25 of the governor shaft 22 are separated, and the pump chamber 4 and the feed pump upstream. (low pressure side) is cut off, and the pressure inside the pump chamber 4 increases.

Along with this, the pressure in the second hydraulic chamber 52 of the timer 44 also increases, so the timer piston 46 moves toward the advancing side against the elastic force of the spring 49.

On the other hand, when the engine is operated at a high altitude where the atmospheric pressure has decreased, the atmospheric pressure detection switch 60 is turned off, so the solenoid valve 28 is not energized and the relief passage 27 is closed.

As a result, the pressure inside the pump chamber 4 does not decrease, and the fuel injection timing is maintained at the advance side without delay even during low and medium loads, as in the case of high loads.

Therefore, even if the ignition delay time increases, a good combustion state can be maintained and half-misfires can be prevented.

Figures 3 and 4 show the above operation in terms of the relationship between engine load or engine speed and fuel injection timing.
It is a diagram.

First, FIG. 3 shows the relationship between the load and the injection timing when the engine speed is constant, with the solid line A showing the change at level ground, and the broken line B showing the change at high ground.

Further, in FIG. 4, the solid line C shows the change at high loads on flat land and at high altitudes, and the solid line C shows the changes at low and medium loads on flat land.

In the above embodiment, the relief passage 27 is completely closed during operation at high altitudes where the atmospheric pressure is reduced, but the passage area of the relief passage may be reduced to a set amount.

Alternatively, the passage area of the relief passage 27 can be
The passage area of the relief passage may be made variable according to the expansion and contraction of the relief passage, so that the passage area of the relief passage decreases as the atmospheric pressure decreases.

The degree of reduction in the passage area of the IJ-IJ-fu passage may be set within the injection timing range that allows for good combustion at low loads at high altitudes.

As described above, the present invention reduces the oil pressure lowering function of the hydraulic control device that delays the fuel injection timing by reducing the oil pressure acting on the injection timing adjustment device when the engine load is small, so that the oil pressure reduction function is reduced when the atmospheric pressure decreases. Because of this structure, even if the ignition delay time increases at high altitudes, the fuel injection timing can be easily corrected to the advanced side, resulting in good combustion and preventing half-misfires, which has excellent practical effects. It is.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings illustrate an embodiment of the present invention, in which FIG. 1 is a longitudinal sectional view of a fuel injection device for a diesel engine, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. The figure shows the relationship between the engine load and the fuel injection timing, and FIG. 4 shows the relationship between the engine rotation speed and the fuel injection timing. 1: Distributed fuel injection pump, 7: Plunger, 9: Cam disc, 10: Roller holder, 23: Governor sleeve, 24: Relief port, 27: Relief passage, 28:
Solenoid valve, 44: Timer 60: Atmospheric pressure detection switch, 6
3: Bellows.

Claims (1)

[Scope of utility model registration request] A cam device that reciprocates a plunger that pumps fuel; an injection timing adjustment device that adjusts the fuel injection timing by operating the cam device with oil pressure corresponding to the engine rotation speed; and lowering the oil pressure when the engine load is small. A fuel injection device for a diesel engine is provided with a pressure detection device for detecting atmospheric pressure, and the pressure detection device is provided with a pressure detection device for detecting atmospheric pressure, and the pressure detection device is provided with a hydraulic control device for delaying the fuel injection timing. A fuel injection device for a diesel engine, characterized in that a restraint device is linked to reduce a hydraulic pressure lowering function.